Cooling techniques for enhancing of photovoltaic cell efficiency: Review

The current energy requirements are mostly met by fossil fuels and non-renewable sources which are depleting at rapid rate besides being emitters of greenhouse gases, so the solutions depend on renewable energy. Solar energy is one of these clean renewable energies, that are inexhaustible and has no emissions. The solar radiation falling on the photovoltaic cells, part of it converted into electrical energy and the other part of this radiation converted into heat, which causes decrease in the efficiency of the photovoltaic cell. In general, the performance of photovoltaic cells decreases by 0.5% for each degree of temperature rise, and this depends on the type and material of photovoltaic cells used. Therefore, it was necessary to solve this problem by controlling the operating temperature by various cooling techniques, especially in areas with high temperatures, in order to increase the efficiency of photovoltaic cells. This work, has been reviewed the studies and research conducted in recent years on cooling techniques and controlling the operating temperature of photovoltaic cells and analyzed the results. These methods include natural air cooling, forced air cooling, passive water cooling, active water cooling, and pcm cooling. The results showed that forced cooling methods (forced cooling with water or air) are more efficient than passive methods, as expected. However, active cooling methods require costs for construction and maintenance, in addition it consume energy, so it is possible to replace passive cooling instead of active cooling because passive cooling may lead to more energy gain in some cases than active cooling if the energy consumed for pumping in the active cooling is taken into consideration and reduce the costs. The using of hybrid cooling photovoltaic / thermal system (pv \ t), the active cooling is better than the passive cooling because the heat rejected can be used. As for areas that have very hot climate, it is preferable to use front cooling with water, as it considered more economical. Cooling with phase change materials increases the efficiency of energy production and also gives an opportunity to use thermal energy. But this method is less efficient of other methods and the cost of installing it is high.